Marking fused bifocal lenses for identification



May 3, 1927.

G. A. CLEMENT MARKING FUSED BIFOCAL LENSES FOR IDENTIFICATION Filed Aug. 13. 1925 INVENTOR. /Z- 4 M A TTORNEYS ian 3, 1921. 1

{UNITED sra'rrs PAT N OFFICE.

1 Gannon n. ennnnnr, or zoom var-non, nnw'yoax.

BRING IUSED BII'OCAL LENSES FOB IDENTIFICATION.

i application use Au ust ,1a, 1925. Serial n. 50.08;. V

returned for credit, will be eliminated if the identifying marks are of such'a character or are so disposed that they are not eradicated by the grinding and polishing operations.

My invention has to do especially with.

the identification of fused bifocal lenses and blanks therefor, and its object primarily is to provide a mark for such lenses and blanks Wl'llCll remains in the finished lens and yet is not visible to the ordinary observer and.

a does not interfere with the refractive or translucent character of the lens. Another object is facility and inexpensiveness in introducing the identifying marks. general objects, such as permanency of the mark, freedom from interference with the vision of the wearer, arfd facility in recognition and identification will appear from the following particular description.

Fused bifocal lens blanks are made by fusing a small glass segment of one index of refraction on to a large glass blank of another index of refraction. Ordinarily the major lens blank is crown glass and the mi-. nor lens blank or so ent 1s flint lass. A seat/for the se ment is formed on t e major blank, either B grinding and polishing a segmental area extending from the edge to near the center of one face of themolded blank, or the seat may be molded on the blank, and one face of the segment is similarly repared for fusing on the seat. The

two e ements are then placed in an oven with the prepared surfaces adjacent and there subjected to heat until fused together. The bifocal face of the blank is subsequently ground and finished down to a continuous unbroken spherical surface including a'portion of the flint segment, which segmental area constitutes the reading field due to the higher refractivity of the flint glass. The

through that portion of the lens.

ably the mark is disposed substantially to of vision through.

Other contact or fusion surface is thus internal'of the finished lens.

In accordance with. my invention I-eause' an identifying mark tobe'made in'this fusion surface, for example, either by molding or scratching it on the contact surface of one of the lens elements prior to fusing them. My usual practice is to scratch the mark lightly on, the finished surface,.of-the I seat on the crown glass blank. I prefer to put it on the major blank since the crown glass has the higher fusing point and the mark is therefore less liable to be obliterated by the fusing. A minute symbol or mark scratched in the highly polished surface will be readily apparent under a magnifying glass, but Wlll not be noticeable either to the wearer of the lenses or to another and will not appreciably interfere with the refraction of the light passing Preferone side of the usual line the readin portion of the finished lens.

In the (ii'awings I have shown my invention, applied to a fused bifocal lens blank. Figs. 1 and 2 are, respectively, a central section and a plan of a major lens blank.

Figs. 3 and 4 ar ton or segment. 1

Fig. 5 is a centr'al'section of the fused blank.

Fig. 6 is a plan of the finished lens made from the blank.

Similar views of a but- The major lens blank is shown of eriscopic form and is commonly made by ropping or molding. This blank is composed of crown glass and has on its convex face a'segmental seat 2 which is usually prepared by grinding and polishing thisportion of the surface of, the molded blank. The curvature of this seat 2 depends upon the added strength which is desired through the reading portion of the finished lens. It is shown as a convex spherical or plus curve but of longer radius than thecurve of the molded surface. On this seat 2 is scratched the identifyingmark, in this case shown as the letters GAO. They are shown as located near the lower ed e of the segmental seat,

being therefore/ cons1derably below the optical axis and/ the usual center of vision through the reading portion of the finished lens. For this rea n the letters will very fore covered by the flint glass.

mamas rarely' come within the line of vision of the wearer of the lens, but the letters are moreover so small and so lightly scratched that they are unobservable to the wearer even when they come within his line of vision.

The segment or button 3 of flint glass has one face ground and polished to the proper curvature, and is then fused upon the seat 2, making the blank as shown in Fig. 5. The bifocal side of the blank will then be groundv down, for example, to the curve indicated by the dotted line in Fig. 5, so as to make a continuous surface including a portion of the flint glass segment. The letters scratched in the seat 2 are there- Finally the opposite side of the blank is ground accord ing to the prescription and the finished lens is cut and edged to the desired shape, for example, as shown in Fig. 6. It will be observed that this brings the identifying letters very close to the lower edge of the segment. It is obvious that the mark may be located elsewhere on the contact surface, for example, near one corner of the segment which very seldom comes in the line of VlSlOIl.

It is also obvious that the mark may be of a. different character than that indicated and may be otherwise formed in one of the contact surfaces, and that the embodiment of my invention as illustrated and above described may be otherwise modified without departing from the principle and scope of my invention as pointed out in the appended claims.

I claim:

1. A. fused bifocal lens or blank therefor having an identifying mark formed on the contact surfaceof one of the fused lens elements.

2. The method of marking fused bifocal lens blanks for the purpose of identification consisting in finishing a portion of one face of a major lens to a given curve as a seat for a minor lens and finishing one face of a minor lens for fusing on said seat,

making an identifying mark on one of the finished surfaces, and then placing the two surfaces together and sub ectng them to heat until fused.

3. The method. of marking fused bifocal lens blanks for the purpose of identification consisting in preparing a seat on a lens of glass of relatively high fusing point, making an identifying mark in the surface of said seat, and then fusing on said seat another lens of lower fusing point.

4. A lens formed of a piece of glass having a depression in one surface thereof and constituting a major lens blank, and another piece of glass filling and fused in said depression in the major lens blank, the adjacentsurface of one of said pieces of glass having a distinguishing mark in it between the two pieces of glass fused together.

5. A lens formed of a major lens blank having a depression in one surface thereof, and another piece of glass filling and fused in said depression of the major lens blank, the depressed portion of said major lens blank having a distinguishing mark in it between the two pieces of glass fused together.

6. The process of making a lens, which process consists in grinding and polishing a depression in a piece of glass to form a major lens blank, forming another piece of glass to fit in said depression, making a distinguishing mark in the adjacent surface of one of said pieces of glass, fusing the two pieces of glass together, and thereafter grinding and polishing the lens.

7. The process of marking a lens, which process consists in grinding and polishing a depression in a major lens blank, marking the surface of the depression as desired,

. filling said depression with other glass, fusing the same with said major blank, and thereafter grinding and polishing the lens.

In witness whereof, I hereunto subscribe my signature.

GEORGE A. CLEMENT. 

